Installation & Quick Start
This page indicates how to install and quickly begin using TetherCAD.
TetherCAD can be installed using the setup.py file included. Simply clone the repository, move to the repository folder and install using the setup.py file to install the library directly on your system or within a virtual environment. If an error is encountered where setuptools is missing, then this package should be installed and before the python setup file. Installing within a Python3 virtual environment is recommended.
To install the library within, clone it to a folder, move into the folder and run: pip3 install .
TetherCAD is best used within standalone Python scripts or Jupyter notebooks. The following subsections show examples of defining simple geometries and using them in analyses. The operation of the classes and functions used in these examples are explained in more detail during the Usage and Design sections of this wiki page.
A piece of simple example code building a tether is shown below:
from tether_analysis.TetherDesign import Layer, Wire, RoundTetherDesign
# Construct a kapton insulated copper wire
conductor = Layer("copper", "Conductor", 0.25)
insulator = Wire("electrical", "kapton", "Kapton Wire", 0.15, innerLayer=conductor)
# Arrange the wires in a list
wireList = [insulator, insulator, insulator, insulator]
# Build the layers of the tether
core = Layer("fep", "Core", 0.25, color="black")
memLayer = Layer("fep", "Wires", 0.1, innerLayer=core, memberList=wireList)
strength_layer = Layer("vectran_kuraray_ht", "strength_layer", 0.15, innerLayer=memLayer)
abrasionLayer = Layer("ptfe", "abrasion", 0.2, innerLayer=strength_layer)
# Pass to a tether design object
tether = RoundTetherDesign("Example", abrasionLayer, 100)
tether.illustrate()
tether.tetherDetails()
This code starts by importing necessary classes and then by building a simple Kapton insulated wire. This wire has an outer layer Kapton which is 0.15mm thick, and an inner conductor layer of Copper which is 0.25mm thick.
It then creates a list representing four of these wires for use within the tether design.
Next the code sets up the core layer, the inner most layer of the tether. It is a layer made of FEP, with a thickness of 0.25mm, and has its color set to black to distinguish it from other FEP layers.
A layer of FEP containing members (default colored) is then placed around the core layer, with a thickness of 0.1mm The list of wires are passed as an argument, and the layer is sized appropriately to fit them evenly spaced. The thickness for this layer is increased from 0.1mm to a larger quantity to support the size of the wires.
The last two layers: strength and abrasion, are placed around the existing layers following the same format to finish the cross sectional design.
This design is then given as an input to a RoundTetherDesign object, which provides additional context such as the length, and computes the mass. Here we pass this tether object a name of "Example", the uppermost layer within our tree: abrasion and give it a length of 100m.
Using the new tether object, the tether in its entirety can be visualized and we can print out its outer diameter, radius and mass.
A piece of simple example code running a power analysis is shown below. Note: This code uses the tether design shown in a previous example.
from calculation_libraries.PowerAnalysis import dc_power_transmission_analysis
pathList = tether.findWires("electrical")
send_paths = [pathList[0], pathList[2]]
return_paths = [pathList[1], pathList[3]]
efficiency = dc_power_transmission_analysis(tether, 500, 1000, send_paths, return_paths, True)
First, this code imports the DC power analysis function: dc_power_transmission_analysis.
It then identifies the "paths" of all electrical wires within the tethers. When a layer tree is given to a RoundTetherDesign object, it initializes a unique path string for each layer in the tree. This path is used to identify the layer by other code such as analyses.
These paths are split into lists to indicate which wires should be used for the send and return paths of the transmission line.
The dc_power_transmission_analysis is then called, passing tether object, a line input voltage of 500V, a desired power transmission of 1kW, the lists of send/return paths, and a boolean whether to output transmission information.
The tests for the system are built using pytest, and can be run from within the tethercad/tests folder using the command:
python3 -m pytest <test_filename>.py. At the moment, running tests from outside this folder does not work due to pathing with the test databases.
As of writing there are three test files:
- test_analyses.py
- test_databases.py
- test_tether_design.py
From within the tests folder, the command to run all three would be: python3 -m pytest test_analyses.py test_databases.py test_tether_design.py.
The first file tests the set of analysis functions, verifying that the results look correct.
The second tests that the database system is functioning properly, performing the correct conversions and pulling correct database values.
The final tests the geometry system, ensuring that the tether is being correctly constructed and errors are correctly identified.